A thermosiphon is a method of passive heat exchange between the heat source and the heat sink. In the case here the engine is the heat source and the water tank is the heat sink.

whippet coolant system

The fundamental issue when running the Whippet engine in this configuration was it was getting hot and the water was remaining cool.

Note: this engine was given to us for review by

idea for modifying the cooling system to thermosiphon

A thermosiphon needs the heat source to be lower than the heat sink. The heat flow can then go up the pipe and into the top of the cooling tank.

The hot water cools down and sinks in the tank. This cool water flows into the lower connection point on the engine.

Whippet coolant tank - thermosiphon

Compared to the original design you can see that:

  • Cooling tank lifted 21mm up
  • Hot pipe into the tank was moved up ~10mm on the side of the tank
  • Cold outlet pipe was moved to the bottom of the tank.

The water level is kept above the highest connection point on the tank and hence above the engine.

Running this engine I now get a thermosiphon, the engine runs cooler and the water in the cooling tank gets hot. You can feel a temperature gradient from top to bottom of the cooling tank.

enjomor whippet engine

Running the Enjomor Whippet

Running the Enjomor Whippet on glow fuel. I’ve made a cooling tank, part made a fuel tank and the engine is fix to an oak base. Before going too much further I really wanted to run this little engine.

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